The present invention relates to thioesters which are particularly useful as synergists when used with conventional phenolic and amine antioxidants.
In addition, the present invention relates to a two component stabilizer system for polymers.
Ester materials have been used as synergists in combination with free amine antioxidants and phenolic antioxidants. For example, U.S. Pat. No. 4,216,116 discloses a stabilization system for organic materials comprising a phenolic antioxidant and a polyethyleneoxy diester of a thiopropionic acid. Also, see U.S. Pat. Nos. 4,125,515, 4,241,217 and 4,301,296 which teach the combination of conventional free amine antioxidants with esters which function as synergists, for example, 3,6,9-trioxyaundecane-1,11-bis (3-n-dodecylthio-propionate). Whereas, the esters described in these patents have become commercially available products sold under the trademark Wingstay.RTM. SN-1 by The Goodyear Tire & Rubber Company of Akron, Ohio, those skilled in the art are constantly searching for new, improved antidegradant systems to further prolong the life of polymer products. Therefore, there exists a need for compositions which are useful in further prolonging the life of polymers and in particular, rubber compositions.